Whale sharks (Rhincodon typus) are the largest fish in the sea and are a big attraction for divers and snorkelers here in Thailand. We get countless requests from people wanting to scuba dive with a whale shark.
With a lifespan of well over 50 years whale sharks can grow to be huge, up to 12 meters in length weighing a whopping 20 tonnes. In fact, the biggest recorded whale shark was a gigantic 20 meter long individual back in 1987 off Tasmania, Australia. Most of the whale sharks we see off Koh Tao are more modest, typically 5-8 meters in length (which is still a truly massive fish).
Despite their huge size, whale sharks pose no real threat to divers. Usually slow moving and docile, the species have vast wide mouths at the front of their head (typically 1.5 meters across) which they use to filter feed on small marine species. They suck water into their mouth and filter out all the miniscule organisms, using around 300 tiny hooked teeth. Whale sharks’ diet typically consist plankton and small fish (krill, larvae, jellyfish, anchovies, juvenile tuna, squid etc).
Rather than staying in one spot, whale sharks are a migratory pelagic (open sea) species found in tropical seas. Whilst often seen feeding in shallow waters, they can dive very deep, up to 1700 meters below the surface. Whale sharks are generally solitary though much larger groups of around 100 have been spotted feeding together.
Due to their vast size whale sharks have few predators in nature. But like many animals, human encroachment has impacted the whale shark population, severely reducing their numbers. Sometimes this is accidental; Entanglement in fishing lines or nets, collision with a boat or propeller cut. Whale sharks are considered a food in some countries, with many reported cases of finning. Not to mention the effects of ocean pollution.
As such, whale sharks carry a global conservation status of ‘vulnerable to extinction’ and are a protected species in many countries, (including Thailand).
As discussed above, whale sharks are usually docile and slow moving. Provided we follow a few simple guidelines whale sharks pose no threat to threat to divers and an underwater encounter can be a truly incredible experience. In fact, we seen many occasions where whale sharks are inquisitive towards divers.
But we must keep in mind – they are huge and powerful – so it’s important to treat whale sharks with respect. Plus as an endangered species we have a duty to ensure whale sharks stay safe too.
So a few guidelines to follow if you are lucky enough to spot a whale shark:
As we already learned, whale sharks are a migratory species and aren’t here all the time.
We do frequently see them migrating through the Gulf of Thailand, spending a day or so feeding around the dive sites off Koh Tao.
Sightings are more common around the deeper pinnacle dives sites (Chumphon Pinnacles, Southwest, Sail Rock), but it can happen anywhere. We’ve encountered countless whale sharks around the shallower reef dive sites too (Twins, White Rock etc).
You just need to be a bit lucky and keep your eyes open.
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